The current technological age is embodied by a constant push for increased performance and efficiency of devices. This push is particularly observable for technologies that involve electron sources, such as spacecraft propulsion, electronic displays, and X-ray sources. Efficiency of these systems can be increased by reducing weight and power consumption, but is often limited by a bulky and energy-hungry electron source.
Most electron sources utilize thermionic emission, which involves heating a metal filament to several thousand degrees Celsius in order to produce electrons. Thermionic emission sources possess inherent inefficiencies because they are relatively bulky and must be heated to very high temperatures, thus consuming more energy. One alternative to thermionic emission is field electron emission (FE), which involves the application of electric fields at room temperature to induce electron emission via tunneling. Normally, large electric fields (hundreds of V μm−1) are needed for FE, but this field is highly dependent on the electron source geometry, where sharp tips can reduce the macroscopic electric field needed. Since no heating is necessary, these sources can be much more efficient and reliable if emission can be achieved at a sufficiently low potential, providing marked improvement over current technologies.
One category of materials utilize devices based on a Spindt cathode designs, where an emitter in a triode device produce electrons in response to a conductive base substrate and a counterelectrode, or gate electrode. Use of sharp tipped nanomaterials such as carbon nanotubes have been utilized in the field emission performance. Initial work by this group has focused on building emitters for use in, for example, cold cathodes.